Neural pathways from the rostral hypothalamus (RH) into the medial basal region (MBH) influence gonadotropin release since RH lesions block and electrical stimulation (ES) causes LH release in rhesus monkeys. Prolactin release is also triggered by ES of the MBH. Estrogen facilitates this electrically induced prolactin release but inhibits the electrically induced LH release. We propose to examine where and how estrogen acts to modulate differently prolactin and gonadotropin secretions. We will compare the effects of various adrenergic blocking drugs, locally infused estradiol-17 Beta, and phenobarbital on estrogen-induced or electrically induced LH and prolactin release in rhesus females. Gonadotropin and prolactin secretions will be determined after ES of intact monkeys with varying ratios of serum estradiol and progesterone. The influence of hypothalamic neurons and ovarian steroids on gonadotropin and prolactin secretions of pituitary cells grown in culture will also be assessed. Finally, we will examine the hypothalamic regions and ovarian hormone influence on selective FSH secretion in monkeys and hamsters. BIBLIOGRAPHIC REFERENCES: Quadri, S.K., R.L. Norman, and H.G. Spies. Prolactin release following electrical stimulation of the brain in ovariectomized and ovariectomized-estrogen-treated rhesus monkeys. Endocrinology, 100:325-330, 1977. Resko, J.A., S.K. Quadri, and H.G. Spies. Regulation of gonadotropins in gonadectomized rhesus monkeys: Ineffectiveness of testosterone. Soc. for the Study of Reprod. 9th Annual Meetng, p. 86, 1976, Abstract.